Stabilization of rayon cake size before centrifugal washing



y 8, 1953 w. RO BRIEN ETAL 7, 0

STABILIZATIION 0F RAYQN CAKE SIZE BEFORE CENTRIFUGAL WASHING Filid NOV- 9, 1949 7 7 INVENTOR.

WILLIAM RI/JJELL OBRIENand.

BY GE'ORGERANDOLPHJCANTLING ATTORNEY l atented July 28, 1953? UNITED STATES PATENT OFFICE STABILIZATION OF RAYON CAKE SIZE BEFORE CENTRIFUGAL WASHING Application November 9, 1949, Serial No. 126,302

4 Claims.

This invention relates to an improvement in the processing of Viscose rayon yarn. More particularly, this invention relates to amethod of stabilizing the size of cakes of viscose rayon yarn, especially high tenacity yarns, after doffing the acid cake from the spinning bucket and prior to washing.

When viscose rayon yarn is spun into a spinning bucket, the cake doffed generally contains somewhat more than its own dry weight in spinning bath. An analysis of this liquor contained in a freshly spun cake will show it to contain about sodium and zinc sulfate, 3% sulfuric acid and the balance water, even when the yarn is passed into hot-dip baths containing primary bath diluted with 3 to 4 parts of water for the final stretching operation. The presence of the relatively high salt content in this cake liquor maintains the acid gel yarn in a relatively low state of swelling. Consequently, when the cake i subjected to washing with water, immediate dilution of the salt solution in the cake takes place and brings about very substantial swelling of the yarn. In swelling, the yarn shrinks in length and, due to the angle of lay in the cake, the cake increases in length and diminishes correspondingly in circumference. This change in size is immaterial if the cake is subjected to pressure or drip washing, but when washing is to be done centrifugally in individual buckets, a num- 'ber of deleterious results arise.

Rayon yarn cakes spun as above set forth will shrink in the neighborhood of 2 to 3 in circumference between the time of doffing from the spinning bucket and completion of washing. When such cakes are charged into individual centrifugal washing buckets, they shrink during the early stage of washing and become loose in the bucket causing the bucket to wobble excessively by unbalancing the load. Wobbly buckets cause many wraps on the centrally located spray nozzles and result in many motor and spindle failures thereby excessively increasing maintenance costs and greatly reducing the proportion of first quality yarn.

It is customary in the industry to utilize tapered wash buckets to fit the tapered contour of the cakes snugly and balance the load as nearly as possible. However, when the cake shrinks after the washing operation has begun, the cake is held against one side of the bucket because of imperfect balance and is prevented from settling snugly into the tapered bucket. The greater the shrinkage of the cake after the washing operation begins, the greater will be the resulting unbalance.

' correspond to the spinning cycles.

It is also well established that gel cakes of acid yarn, particularly high tenacity yarn, gradually shrink in size on standing prior to Washing due to slow chemical and physical changes in the freshly spun yarn. The shrinkage is very slow and is not sufiicient to prevent shrinkage during washing. In practice it is customary to maintain a supply of acid cakes ahead of the washing operation, because the washing cycles do not Thus, cakes vary in size depending on aging prior to washing. Because of this variation in size some cakes fit deeply into the tapered buckets while the larger ones are supported higher in the bucket. This difference in height requires that the purification solutions be applied over the extreme ranges in height and results in their being wasted.

Furthermore, those .cakes which have not shrunk sufficiently prior to insertion in the bucket will shrink excessively after washing has begun and cause excessive unbalance. This results in equipment failure and the compacting eiiect of the unbalanced load plus the poor distribution of washin liquor leads to improper purification and disruption of the yarn windings. A second cycle, often required to complete the washing, further disturbs the windings and results in losses of winding efiiciency'and increases the waste.

In many cases the wobble increases progressively until the solution applicator inside the hollow cake strikes the yarn causing it or the protecting knitted cloth sleeve, if one is being used, to wrap around the stationary applicator either ripping it off or burning out the motor. In these cases both the cake of yarn and the equipment are ruined. Indeed, these difliculties in yarn quality and maintenance costs are generally high enough to make centrifugal washing economically unattractive.

That the abuse of the cakes taking place in centrifugal washing under the conditions metioned above is real and that irreparable damage.

is done to the yarn can better be understood and appreciated if consideration is given to subsequent processing of theyarn. In connection with high tenacity yarn destined for use in the tire industry the yarn is most economically Wet creeled from the washed cakes, passed over hot slasher drums and the large number of ends wound simultaneously at high speed onto a beam. If the yarn windings in the washed cake have been disturbed, repeated breaks will result necessitating stopping the wind-up beam each time a break occurs. Not only does the winding efiiciency go down rapidly, but the quality of the yarn wound up is below standard. Additionally,

degradation of the yarn that results from the mal-washing process contributes very considerably to lowered winding efdciency and poor quality.

It is, therefore, a main object of this invention to reduce to a uniform size all the acid rayon yarn cakes subsequent to doffing them from the spinning buckets and prior to introducing them into the centrifugal washing buckets. It is a further object to provide means for adequately supporting an unwrapped cake. A still further object is the provision of a means for washing unwrapped cakes in a manner whereby the cake size is stabilized prior to washing. Other objects will appear hereinafter.

This invention comprises wetting the acid yarn cake under controlled conditions so as to insure uniform and complete penetration of a considerable amount of water into the cake without disturbing the lay of the yarn, thereby effecting from the cake and a relatively short period of time for equalizing the distribution of water within the cake to effect substantial shrinkage of the cake without causing deleterious shifting of the yarn windings. Control of such factors as amount of water applied, drip application and time lag are of primary importance.

This invention will be better understood by reference to the following figures of which:

Figure 1 is diagrammatic View of the peg conveyor and the drip pan showing the relationship of these to the cakes;

Figure 2 is a plan view of the drip pan;

Figure 3 is a side view taken on 3-3 of Figure 4 of a ribbed belt conveyor carrying a cake and Figure 4 is an end view, in section, of the ribbed belt conveyor showing the unwrapped, supported cake of Figure 3 in a side view.

Only after trying numerous schemes was a satisfactory process developed. Many attempts to spray the cakes caused localized soggy spots resulting in excessive disruption of the yarn windings, while other methods such as an atomized or fog spray failed to wet the arn sufficiently and/or uniformly to bring about the desired shrinkage of the cake within a reasonable period of time. Immersion of the cake is entirely unsatisfactory because such treatment seriously disrupts the cake especially on the outside so that further handling disrupts the yarn windings hopelessly. Notwithstanding these many failures, by proper selection of critical conditions, it was demonstrated that acid cakes of rayon yarn could be wet out satisfactorily in about one minute. When a minimum of minutes lag time was allowed before charging these cakes to the centrifugal washing buckets (for draining of excess water, equalization of the water throughout the cake, yarn swelling and cake shrinkage), to 90% of the shrinkage that would normally occur between doffing and the completion of washing took place. This order of reduction of shrinkage permits satisfactory operation.

In the selected, critical conditions a conveying system may conveniently be used and advanced at a suitable speed in combination with its length to give the desired time of treatment. In Figure l a peg conveyor I is shown which is most satisfactory as it affords free drainage of the Wet cakes and inherently avoids any possibility of wet soggy spots such as would result from the cakes resting in a pool of water. The cakes '2, which may be wrapped but are preferably unwrapped, containing a split spring insert 3, are mounted on the pegs 4 of the conveyor. Free drainage is provided for and the water runs around the outer surfaces and off the bottom as well as through the cake. A drip pan 5 is shown located only slightly above the uppermost part of the cake to avoid any substantial velocity being developed by the water streams issuing from the pan. This distance X should be no more than 2 inches and may be only enough to provide adequate clearance, say inch. The water depth Y in the pan is preferably held to 1%; inches to provide a uniform low head and the 0.063 inch diameter holes are spaced as shown in the Figure 2 formed with a countersink on the top side to provide for better continuous flow of water therethrough. The holes in each row are about 1 inch apart and the rows are about 2 inches apart. The holes in a given row are not aligned with those in each adjacent row, but lie as shown. The stream must be steadily and uniformly applied and have no substantial force which would disrupt the windings. However, it must also have a penetrating ability, not possessed by atomized or fog spray. With the above arrangement of water head pressure, pan location and hole size and distribution, the essential elements are present. Adequate penetration results from the sufiicient mass of water falling on the cake. The cakes move in the conveyor in the direction shown in Figure 1 so that they are exposed to the drip for an optimum time period, about 1 minute, and are allowed to drain freely for a controlled time, about 15 minutes. The length of the conveyor and the length of the drip pan are suitably adjusted. The drainage is collected in a trough (not shown).

In Figures 3 and 4 there is shown a cake 2 supported on its side on a conveyor belt 1 which belt is provided with laterally extending ribs 9 to give satisfactory drainage. The cake 2 is supported by the split spring perforated insert 3 which perforations 8 extend from near one end to near the other end. This sleeve 3 extends beyond both ends of the cake and supports the cake during washing and creeling. The insert has sufficient springiness to exert pressure against the inside walls of the cake, thereby flexibly supporting it, and the insert has sufiicient holes to permit free flow and drainage.

To illustrate further this invention the following Table I of results was obtained under varying conditions of time of drip application, time of lag, temperature of the Water and rate of water flow to a single cake with cake shrinkage results measured around the large end of the cake. In all these tests the cakes used were uniform in size, being about 3.0 pounds (dry weight), and the yarn therein was about 1650 denier when dry. The yarn was spun in a sulfuric acid, sodium sulfate bath containing a small amount of zinc sulfate, hot-dipped through a second bath made up of the primary bath diluted with 4 parts of water and stretched to give a thread tension of .70 gram per denier, then delivered at a rate of yards per minute to an 8 inch diameter spinning bucket rotating at 7500 R. P. M. The size of the cake as spun will vary slightly but is approximately 24% inch.- es in circumference at the large end. The shrinkage that normally occurs between this size at doffing and after completion of centrifugal washing is about to of an inch or from about 2.6 to 3.1%. From the data given below it will be seen that the wetting out treatment causes an initial shrinkage before introducing the cake into the Washing bucket of from about 29% to 94% of the total, overall shrinkage. is preferred that conditions be so adjusted to give an initial shrinkage before the cake is intro duced into the washing bucket of at least 50% of the total eventual shrinkage.

plicatlon for aperiod or 5 minutes or longer or to reduce the time of water application to 30 seconds or less. If the water temperature is increased above 35 0., increased shrink-age takes place. Nevertheless, good results can be'secured with 'room temperature water and, if desired, the water may be heated as high as 60 or even The process of this invention is not a washing process. Very little of the salts and acid in the freshly spun cake are removed by this process. By this invention cakes are uniformly preshrunk a large portion of their total possible shrinkage prior to the centrifugal washing without cake or yarn damage. With this controlled stabilizing of the cake size, one may proceed with the centrifu- Table I Rate of Cake Circumference at Large End, in Inches g Percent T t fi g Water Temp. Total Iggg Shrinkage Nes 0 dine Flow per Water Shrinkage, and g After 1st Cake, C. As After After T me Lag After In Inches w Lag of Lbs/Min. Sp Mins. Lag Indicated Washing as mg Total 2. 16 35 24. 24. 06 66 19 29 8. 58 24. 25 23. 94 66 31 47 2.16 35 24. 25 23. 94 66 31 47 2. 16 35 24. 25 23. 94 66 31 47 8. 58 35 24. 25 23. 94 66 31 47 5. 06 35 24. 31 28. 87 66 44 67 7. 26 35 24. 25 23. 75 66 l 50 76 13. 86 35 24. 31 23. 81 66 50' 76 7. 26 24. 31 23. 69 66 62 94 35 2i. 25 23. e1 23. e9 44 e4 35 24. 1.9 23. 81 U. 23. 56 63 38 O) 20 24. 25 23.75 after 1% hrS 23. 56 69 50 72 35 24.12 23.62 after 2% his. 23. 50 .62 i .50 76 1 Approximately 2.5lbs. /n1in.

2 Figure 0.66 is average of measured values. 1

From the above results it can be seen that a preferred set of conditions for stabilizing cakes of the s'me and yarn denier tested are:

1. A delivery of about 5 pounds of water per minute to each cake, the water being heated to from 35 to 50 C.

2. The period of time of water application should be at least 1 minute.

3. The time lag after wetting and before centrifugal washing should be at least 15 minutes.

In order to get these conditions, the drip pans have holes distributed as shown in Figure 2, the holes being 0.063 inch diameter and countersunk, and the water head in the pan is kept constant at 1.25 inches and the bottom of the pan is placed no more than 2 inches above the cake.

With other cake and/or yarn sizes the above preferred conditions will need to be modified somewhat for optimum results. It is essential that the water be well distributed over the cake, that only enough water be applied so that the cake does not become soggy and that the water he applied gently to prevent disruption of the windings. By means of the perforated sleeve insert, the peg conveyor or the like and the drip application, all of this invention, these objectives are accomplished. In general, a long lag time, that is an hour or so, after stabilizing the cake will not help much nor a substantially higher rate of water application for a correspondingly shorter period. The lag time may be increased to several hours without harmful effect or may be shortened slightly, say to 10 minutes, without substantial change in the amount of cake shrinkage. Higher flows generally are ineffective because the cake cannot absorb the Water much faster and higher rates of drainage cause more disruption of windings. In some instances it gal Washing by merely inserting the supported cake in the bucket and spraying water against insert 3 as the bucket rotates. The wash water is forced through perforations 8 and into the cake. Objectionable unbalance is avoided.

Through the'use of this invention it has been possible to attain unusually high washing efficiency and the production of washed cakes that unwind well in wet creeling to a slasher and yarn of high quality with good physical properties. In fact, yarn processed as above described has proved far superior in ease of handling and in yarn quality to yarn similarly spun but treated with Water in going over the last feed wheel or as it is being collected in the spinning bucket. While satisfactory washing without pre-shrinkage can be attained as by water treatment at the feed wheel, such procedures cause looser formation of yarn at the inside of the cake which 'results in running diificulties in the slasher operation. Furthermore, because of this invention there is no excess water from the spinning machine to be evaporated in the recovery of bath as would result if either of the alternative shrinking methods just mentioned was used. In previous methods involving the treatment of cakes which were not given the pre-shrinkage of this invention, from 5 to 10 times as many incompletely processed cakes were obtained than obtained in the same treatments involving cakes pre-shrunk by the process of this invention. Further, many more conventional cakes were bruised and torn up in the Washers than were the pre-shrunk cakes.

Freshly spun cakes of acid yarn slowly release gaseous CS2 and H23 to the atmosphere on standing. Since both of these gases are poisonous, much attention and great expense in equipment is required to provide sufficient fresh air may be advantageous to continue the drip ap- 78 to dilute the concentration of these gases to a safe limit-for personnel. working'inthe vvicinity of these cakes. Because CS2 is released in much larger quantities most of the attention is directed toward its control. The quantity of CS2 released from a 3.0 pound cake of freshly doffed viscose rayon spun under the above described conditions may be determined by analyzing the air exhausted from an enclosure containing a cake around which air is passed at a constant rate. The rate of evaporation of CS2 may be substanw tially reduced by stabilizing the cake in the manner described above. This is illustrated in the following table which shows the concentration of CS2 in air exhausted at a rate of 17.5 C. F. M. from a single cake contained in an enclosure:

Stabilized Normal Cake Cake Parts/million CS; in air 20 min. after cake is o e 300 920 Parts/million CS2 in air 30 min. after cake is o e 280 690 Parts/million CS1 in air 60 min. after cake is dolled 235 355 in enclosures where the CS2 may be readily han-.

dled or even recovered depending upon the process used.

Any departure from the procedure described herein which conforms to the principles of the invention is intended to be included within the scope of the claims below.

We claim: 1. A process for wetting out and circumferentially shrinking an acid rayon yarn cake which comprises flexibly supporting said cake internally throughout its length; gently showering the outer wall of said supported cake with about five pounds per minute of water for, about at least, one minute, said water being in the form of an evenly distributed steady, uniform stream; and permitting the resultant showered cake to drain freely.

2. A process in accordance with claim 1 in which the said water is heated to about 35 C. to about 50 C.

3. A process in accordance with claim 1 in which the said cake is permitted to drain freely for, at least, fifteen minutes.

4. A process in accordance with claim 1 in which the said water is heated to about 35 C. to about 50 C. and the resultant showered cake is permitted to drain freely for, at least, fifteen minutes.

WILLIAM RUSSELL OBRIEN. GEORGE RANDOLPH SCANTLING.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,688,702 Gladding Oct. 23, 1928 1,736,681 Topham Nov. 19, 1929 1,767,294 Landeskroener June 24, 1930 1,817,576 Monkmeyer Aug. 4, 1931 1,973,953 Gordon Sept. 18, 1934 2,042,529 Huttinger June 2, 1936 2,053,293 Long Sept. 8, 1936 2,058,576 Dulken Oct. 27, 1936 2,091,725 White Aug. 31, 1937 2,130,791 Dunham Sept. 20, 1938 2,243,000 Brown May 20, 1941 FOREIGN PATENTS v Number Country Date 478,219 Great Britain Jan. 14, 1938 

1. A PROCESS FOR WETTING OUT AND CIRCUMFERENTIALLY SHRINKING AN ACID RAYON YARN CAKE WHICH COMPRISES FLEXIBLY SUPPORTING SAID CAKE INTERNALLY THROUGHOUT ITS LENGTH; GENTLY SHOWERING THE OUTER WALL OF SAID SUPPORTED CAKE WITH ABOUT FIVE POUNDS PER MINUTE OF WATER FOR, ABOUT AT LEAST, ONE MINUTE, SAID WATER BEINGIN THE FORM OF AN EVENLY DISTRIBUTED STEADY, UNIFORM STREAM; AND PERMITTING THE RESULTANT SHOWERED CAKE TO DRAIN FREELY. 